Can you change gear ratio (and add LSD) on a D70u rear end?

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Can you change gear ratio (and add LSD) on a D70u rear end?

Postby Begle1 » Mon Aug 17, 2020 5:21 pm

Nowadays I have some money and live on an island with no speed limit above 55 mph. There is a 1/4 mile dragstrip however.

I have a mind to go to a greater-reduction rear end and limited slip at the same time. I currently have the 3.07 D70u.


Instead of finding a whole new axle, would it be possible to bolt something like a 4.11 LSD ring and pinion into my D70u? I've heard that the 3.07 ratio can't work in a D70, but I've never heard about somebody trying to go the other way.

Anybody know if I have any options?
1990 D-250 Regular Cab: Tweaked injection pump, built transmission, a cataclysmic charlie foxtrot of electronics, the most intense street-ran water injection system in the country, and some more unique stuff.
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Begle1
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Re: Can you change gear ratio (and add LSD) on a D70u rear end?

Postby Philip » Tue Aug 18, 2020 6:40 am

To change the ratio in that axle would require quite a bit of machine work. The pinion is offset to the ride side about 5/8" for the larger pinion need for that ratio. The has been one person I know of that has regeared an axle to 3:54's. That was many years ago on TDR website.

If you could find a ring gear spacer you could do it. I am not sure if they are made anymore. Might call randy's ring and pinion. They would know if a spacer.
93 W350 Club/cab w/duals, buckets & console, B&W flatbed, G56, 6 spd, 3:07 rears, gages, HX40/16, 4" exhaust, 6X.018 sticks, rear air ride suspension
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Re: Can you change gear ratio (and add LSD) on a D70u rear end?

Postby Begle1 » Tue Aug 18, 2020 11:25 am

Thanks Philip!

Sounds like not worth doing. I'll call Randy's at some point just to see what they say regardless.
1990 D-250 Regular Cab: Tweaked injection pump, built transmission, a cataclysmic charlie foxtrot of electronics, the most intense street-ran water injection system in the country, and some more unique stuff.
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Begle1
14mm rotor
 
Posts: 1964
Joined: Sat Jan 06, 2007 5:31 pm
Location: Kihei, Maui, Hawaii
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Re: Can you change gear ratio (and add LSD) on a D70u rear end?

Postby Philip » Wed Aug 19, 2020 6:05 am

A ring gear spacer is the best option. I don't know if they make them for the 70's anymore.
93 W350 Club/cab w/duals, buckets & console, B&W flatbed, G56, 6 spd, 3:07 rears, gages, HX40/16, 4" exhaust, 6X.018 sticks, rear air ride suspension
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Philip
14mm rotor
 
Posts: 1954
Joined: Mon Jan 08, 2007 10:50 am
Location: Indiana
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